November 14, 2010

Felipe La Rotta from Engallamientos de La Rotta has built a number of cool DIY projects, this DIY Bench Power Supply is one of my favorites. Everyone who is tinkers with electronics will eventually need to progress from a battery as a power supply to a plug in wall wart then eventually to variable supply. This DIY supply quite a good variable supply since it is based on a computer power supply that can supply tons of current at quite a stable voltage. It uses a LM317 and a pot to allow a variable output in addition to the fixed outputs. Best of all the finished boxed supply looks great which isn’t always the case with all DIY projects. I can look around and see that lots of my projects that were created for some utility perform well but look like they were made in my basement.

One major problem I see has to do with airflow, while there is a fan present to pull air into the case with the intent of using it to cool some of the various components, there appears to be a lack of venting to allow the subsequently warmed air to pushed out of the case to make room for more fresh cool air.

I did something vaguely similar to this myself but I left everything in the original PC powersupply case, and removed all of the unnecessary wires except for a 12 Volt feed and a 5 Volt feed (and corresponding ground wires), I also only used two jacks (one red and one black) and a toggle switch attached to a couple of 12 Volt Automotive grade relays (30 Amp Rating, salvaged during a walk in a local junk yard) to permit switching the output to the jacks from 12 Volt to 5 Volt (relays are configured to default to 12 volt output to the jacks, switch supplies 12 volts to relays switching them so that they output 5 volts to the jacks when the switch is flipped).

Unfortunately I didn’t have room for meters as well since the PC power supply was a ‘mini’ one from an old HP computer (otherwise I might have been able to mount a couple of meters on the top of the case along with possibly a variable resistor to allow me to ‘dial down’ the voltage if I needed to.

I also left one of the sets of wiring for connecting to drives intact so I can use it as an external powersupply for connecting hard drives to my computer using one of those USB to SATA & IDE adapters,that way if there’s a fault with the drive I don’t risk my computer’s powersupply being damaged or having it decide to trip the breaker in my computer’s powersupply possibly causing my computer to shutdown on me making me lose whatever I was working on on the computer.